Vol. 10(10), pp. 350-379, October 2016 DOI: 10.5897/AJEST2015.2036 Article Number: F4052F660884 African Journal of Environmental Science and ISSN 1996-0786 Copyright © 2016 Technology Author(s) retain the copyright of this article http://www.academicjournals.org/AJEST Full Length Research Paper Evaluation of fluoride enrichment processes in groundwater of Chimakurthy granitic pluton complex in Prakasam District India A. G. S. Reddy1*, D. V. Reddy2, M. Sudeer Kumar3 and P. K. Naik1 1RGNGWT&RI, Raipur, CG, India. 2CSIR-NGRI, Hyderabad; India. 3CGWB, SR, Hyderabad, T. S, India. Received 5 November, 2015; Accepted 11 February, 2016 Hydrogeochemical evaluation of aquifers belonging to Chimakurthy granitic pluton complex reveals wide spatial and temporal variation in F- distribution. F- concentration in groundwater of different aquifers varies from < 0. 50 to 9.84 mg/l. Among three sampled episodes, the mean value of F- is high in July 2010 and 61% of samples have values above maximum permissible limit as per the Bureau of Indian Standards. In April 2008, 44% and in February 2009, 41% of samples were not fit for drinking purposes due to enrichment of F-. Northern half of the area is almost free from F- but south central part, which has witnessed igneous activity with mafic intrusive form the core area of F- mineralization. Cent percent testing of all the groundwater structures in fifteen villages show uneven distribution of F- even - + - within limited terrain. F show close positive correlation with pH (0.57), Na (0.68), HCO3 (0.61) and distinct negative correlation (-0.31) with Ca2+. The groundwater facies is of sodium bicarbonate chloride type, sodium magnesium bicarbonate type and calcium magnesium bicarbonate type. Among 23 analyzed trace elements, Zn is the most dominant (mean 3200 µmg/l). Trace elements concentrations do not exhibit any distinct control over F- contribution to groundwater. F- content in rock samples varies drastically from below detectable limit (BDL) to 492 ppm whereas in soil it varies between (BDL) and 612 ppm. F- concentration of rock-soil-groundwater does not synchronize depicting latter enrichment of F- into formation water. Ratios, indices and plots indicate multiple mechanisms were responsible in F- absorption into groundwater. Water-rock interactions, ion exchange followed by evapotranspiration have facilitated the F- mineralization of groundwater. Na+/Cl- ratio of >1in almost all the samples of three 2+ 2+ + 2+ 2+ 2+ - sampling sessions establish silicate weathering. Ca /Mg , Na /Ca , Ca , Mg and HCO3 ratios authenticate carbonate dissolution is responsible for alkali earths addition. Sodic rich and calcium depleted water together with balanced alkalinity has enabled F- enrichment. Presence of fluorite as accessory mineral apart from occurrence of F- in mineral lattice of biotite, hornblende, muscovite, and pyroxene were the potential sources of F- to the percolating pore waters. Though F- was abundantly available in solid solution the receptive hydrochemical character of solute was governing the F- adsorption which could be one of the strong reasons for uneven distribution of F- with in similar petrological setup. Key words: Water-rock interaction, fluoride, groundwater, Chimakurthy, gabbro, hydrogeochemistry. Reddy et al. 351 INTRODUCTION Fluoride rich groundwaters were attracting the attention scenario of rural and underdeveloped areas reveal that of wide spectrum of scientists’ world over for the past four groundwater in the virgin or less exploited hinterlands of decades. Since supplementing F- to toothpaste or food Indian sub-continent are also highly contaminated in products was stopped in late seventies due to the many hydrological environments both from geogenic and availability of F- in water as well as edible food items, the anthropogenic sources (Reddy, 2014). Excess fluoride studies on enrichment processes of F- in groundwater affects plants and animals also. The effect on agriculture has taken a quantum leap (Handa,1975; Chinoy, 1991; was also evident due to inhibition on plant metabolism Nawlakhe et al., 1995; Sumalatha et al., 1999; Ray et al., leading to necrosis, needle scratch and tip burn diseases. 2000; Dass et al., 2003; Sreedevi et al., 2006; Madhnure In animals also, prominent symptoms of fluorosis were et al. , 2007; Gupta et al., 2005; Raju et al., 2009; Rizwan observed (Brindha et al., 2011). Having understood and and Gurdepp2013). accepted the fact that enrichment of F- in groundwater is Though drinking water often targeted for high ingestion a natural process; the multi-dimensional research is of F- by human beings, food is also an important source polarized on envisaging the absorption processes and of F- which goes unnoticed due to lack of serious studies isolate F- inflicted waters. in this direction. But of-late the research on F- has Though distribution of F- groundwater in space and become a multi-disciplinary topic involving not only time is very erratic and unpredictable, it is predominant in geologists and hydrogeochemists but also biochemists, tropical zones and its adverse impact is distinct in medical professionals and nutrition experts (Susheela undernourished people and those who are below poverty and Das, 1991; Dobaradaran et al., 2008; Takahashi et line (BPL) especially in third world countries. The southern al., 2001; Sharma and Sharma 2004; Shin et al., 1998; India, being predominantly occupied with peninsular Bouaziz, 2006; Toi et al., 2009). Inadequate F- in drinking gneissic complex, is wreaked with F-contaminated waters waters (< 0.5 mg/l) is also a major challenge in many which occasionally include surface waters too. Wide countries as water is the primary source of F- intake. The spectrum of scientists is engaged in sustained research nationwide mean fluoride level in the groundwater on these stressed, fractured granitic aquifers for the past resources in Iran was found to be lower than the few decades. These efforts have resulted in uninterrupted minimum permissible level of 0.5 mg/L (Mesdaghinia et flow of information, creation of baseline data and al., 2010). In some parts of India, fluoride levels are publications. Institutional effort to mitigate the problem below 0.5 mg/L, while in other places, fluoride levels are and for better understanding of the F- enhancement as high as 30 mg/l (Sharma et al., 2011). Excess process is also evident as many premier institutions and concentration of F- either in water, beverages or in food is NGOs are continuously engaged in research on F- a matter of concern to all public health organizations groundwater adopting latest technology. Elevated fluoride content in drinking water resources F- rich groundwater, though available in almost all the have been reported in a number of countries, but in geological horizons even in alluvial phreatic aquifers, but developing countries because of inadequate financial and its concentration is immensely felt in igneous rocks. The technical supports, dealing with this issue have been Prakasam district of Andhra Pradesh is well known for found problematic and sophisticated (Fawell et al., 2006; plutonic complexes which have some of the rare rock Siddique et al., 2006; D’Alessandro, 2006). assemblages including alkaline rocks, grano-diorite and Drinking water is the major source (75%) of daily intake norite, gabbro etc. Occurrence of F- minerals in mafic rich of F-. The severity of injury is determined by duration of plutonic rocks or migmatites is rare. A chance finding of fluoride exposure and concentration (Sharma et al., F- rich aquifers amidst complex igneous rocks is explored 2011). Growing number of disabilities among people further to bring to light the intricacies of F- assimilation in consuming F- rich groundwater, which often encompass groundwater where the F- is present to the extent of hitherto unknown areas, has made the scientists as well 9mg/l. as administrators to focus on genesis of F- into water in Preliminary study in and around Chimakurthy pluton an urge to search suitable remedial measures revealed the presence of F- concentrated aquifers which (Grandjean et al., 1992; Gupta, 2011; Ayoob and Gupta, has called for detail hydrogeochemical studies. On the 2006; Brunt et al., 2004; Currell et al., 2011; Edmunds basis of the previous publication (Reddy, 2014), the and Smedley, 2005; Kumar and Saxena, 2011; Pillai and present study has been extended to 15 villages Stanley, 2002; Rafique et al., 2009; Shaji et al., 2007; surrounding Chimakurhty, in order to investigate the Subba, 2003). Keen assessment of water quality extent and degree of groundwater pollution, and to *Corresponding author. E-mail: [email protected]. Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License 352 Afr. J. Environ. Sci. Technol. evaluate the principal geochemical factors controlling the deeper in bore wells than open wells as they mostly tap - F contamination. All the groundwater structures in groundwater from semi-confined and partly from confined hydrogeochemical processes that are involved are aquifers (Reddy 2008). - selected villages were subsequently tested for F content - which revealed that F rich aquifers occur in isolated patches confining to peripheries of the plutonic complex MATERIALS AND METHODS which is occupied by migmatites and granite gneisses. - Groundwater samples were collected in three different sampling Presence of F -rich groundwater in hitherto unknown